Bluetooth devices such as Bluetooth speakers, smart phones, smart locks, and various smart Bluetooth sensors and wearable devices, have become widely used in many applications. As Bluetooth technology is designed for low power and low cost operation, the communication range of Bluetooth devices is typically quite short. For example, the typical communication range between two Bluetooth devices, such as a smart phone and a Bluetooth Low Energy (BLE) sensor, is limited to tens of meters in open space and a few meters inside a house, and the Bluetooth transmission typically cannot penetrate walls. The short communication range limits the use of Bluetooth devices in scenarios where longer communication range is required.
Conventional schemes to increase wireless communication range typically involve increasing the transmission power or antenna gain on both sides of the radio frequency transmission. However, for Bluetooth devices, especially the BLE sensors and wearable devices, increasing the transmission power or antenna gain of the devices is often impractical and would defeat the design goal of low power and low cost Bluetooth devices. Thus, it is desired to extend the communication range of Bluetooth devices without having to increase the transmission power or production cost of the Bluetooth devices.